• Specific surface area – Area to volume relationship – PIA, BET, NMR methods • Tortuosity – Flow path length to unit length – Resistivity • Pore size distribution – Frequency of given pore size – Capillary pressure Pore structure measurement Pore area frequency As = V =• Measures the volume of physical adsorption of an inert gas (Ar or N2) on the solid surface at reduced P and T. • Adequate for unconsolidated porous systems Pore structure measurement Gas adsorption (BET) *nsA - As is surface area is the effective surface area covered by a molecule of gas, and - n is the number of molecules in the volume of gas to form a mono-molecular layer. grain Gas monolayer• Relationship between specific surface area and grain size from gas adsorption method. • Function of roundness and sphericity • For spherical grains, • General form: where Ksg is effective grain shape factor Pore structure measurement Gas adsorption (BET) gdgvS27.4gdgvS6gdsgKgvS • relies on sophisticated imaging techniques of thin sections to determine surface area X-ray, back-scattered electrons, and SEM are imaging methods currently used. Pore structure measurement Petrographic Image Analysis (PIA) Image showing pore distribution within the field of view. Pores are gray and pore throats are white [Clelland & Fens, 1991].Pore structure measurement Petrographic Image Analysis (PIA) 2D (a) pore and (b) pore throat size distributions [Clelland & Fens, 1991].• The spin-lattice relaxation time, T1, is a property of the rock and fluid wetting the pore surfaces and therefore related to pore size Pore structure measurement Nuclear Magnetic Resonance (NMR) manmrAgvS*ANMR = NMR surface area of dry material, m2/gm ma = grain-matrix density, gm/cc Diagram of pore size on grain surface relaxation [Oilfield Review, 1997]
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